The invention relates to an improved threaded fastener, for example, a bolt or screw and more particularly to the type of a bolt employed in what is generally referred to as a torque nut. Ever since the first use of threaded fasteners there has been suggested numerous ways and means for preventing the inadvertent loosening of the fastener relative to the piece being secured thereby. The very traditional known "lock" washer would be a well recognized example. Another example would be the cutting of a slot into the free end of a bolt where the slot extends coaxially into the center of the bolt.
Even though many of these, and other similar devices and constructions worked reasonably well in certain applications there are certain applications where there exists a real need for an improved means or construction for preventing the fasteners from turning in either direction and losing their desired position and in some cases pre-set critical fastening force or holding power.
An example of such a fastener where the need of an improved locking means may be useful is the torque screw type fastener employing torque nuts of the type illustrated in U.S. Pat. No. 4,622,730. One of the many applications of the torque nuts disclosed in this patent is to secure a roller bearing to the journal of a shaft such as the work roll of a rolling mill.
These bearings are not only very large expensive items but may operate under extremely high load conditions and speeds and wherein during operation there is a great concern that the bearing be kept from over heating. One of the contributing factors of over heating of the bearing is the degree of "tightness" with which the bearings are held on their journals. While it is required that the bearings be held very firmly, they can not be held so firmly so as to create excessive frictional generated heat leading to early bearing failure.
To add to the difficulty, the system with which the bearing is employed and the bearing itself is continuously subject to thermal expansion and dynamic vibrations. Thus there exist a serious need to provide in this and many other cases a screw type fastener useful in a situation where the member being fastened is subject to vibrations and thermal expansion, which will allow a pre-set fastening power or holding position to be maintained. The holding force required may be anywhere between 0 and 100 percent of the maximum holding force the fastener is capable of exerting, but which will still be prevented for turning and hence disturbing the pre-set fastening force.
It should be noted that while the torque nuts of the type disclosed in the aforesaid patent are designed not to come loose and remain tight on vibrating on pulsating equipment this is on the general assumption that the nuts have been fully torqued.